While Passbook integration may seem pointless for an email application, it’s actually very helpful. When someone sends you a Passbook pass via email, you can open the .pkpass file in Sparrow and automatically add it to your Passbook app.

If you’re unaware, Sparrow was originally released for Mac and later brought to iOS this year. After Sparrow was acquired by Google, the developers moved on to work with the Gmail team, leaving Sparrow without support. However, the Sparrow team has seemed to follow through with updating its iOS app to meet iOS 6 and iPhone 5 requirements.

Sparrow for iOS is available via the App Store for $2.99. I personally use Sparrow on both my Mac and iPhone as the user interface is absolutely amazing. Both the Mac and iOS versions are very similar, so you shouldn’t have an issue getting used to Sparrow for iPhone if you’ve used Sparrow on your Mac in the past.